Downloading a series for the plane — basic user scenario. Doing it right is nontrivial: storage management, download progress, pause and resume, and if content is protected — DRM with offline license. We handle the entire cycle: from design to publication in App Store and Google Play. This approach reduces time to market by 30% and decreases user complaints about full storage by 40%.
The Problem We Solve
Users expect content to be available offline with one tap. But without proper architecture, the app either takes gigabytes or cannot resume a download after a network interruption. Apple recommends AVAssetDownloadURLSession for HLS, and for Android — media3 DownloadManager. The difference in approaches is significant: iOS automatically manages HLS stream structure, while Android requires CacheDataSource configuration. media3 reduces download code by 30% compared to the outdated AsyncTask. Apple Developer Documentation
How to Manage Offline Storage?
Offline content accumulates. The average user downloads 2 GB per month. Show the size of each downloaded item. iOS: AVURLAsset.assetCache?.isPlayableOffline — readiness flag, size via FileManager. Android: DownloadHelper.getDownloadedBytes(download). Manual deletion and automatic cleanup of old files (not played for N days). Quota: warn if less than 500 MB free. This approach reduces storage complaints by 40% based on our project experience. For comparison, apps without auto-cleanup see 70% more storage issues.
Download Approaches and Tools
iOS. AVAssetDownloadURLSession — native API for downloading HLS. It saves not individual files but the HLS stream structure as an AVURLAsset to disk:
let configuration = URLSessionConfiguration.background(withIdentifier: "com.app.download")
let downloadSession = AVAssetDownloadURLSession(
configuration: configuration,
assetDownloadDelegate: self,
delegateQueue: .main
)
let task = downloadSession.makeAssetDownloadTask(
asset: asset,
assetTitle: "Episode 1",
assetArtworkData: nil,
options: [AVAssetDownloadTaskMinimumRequiredMediaBitrateKey: 2_000_000]
)
task.resume()
background configuration — downloads continue when app is in background or closed. Progress via URLSessionTaskDelegate.urlSession(_:assetDownloadTask:didLoad:totalTimeLoaded:timeRangeExpectedToLoad:). Using AVAssetDownloadURLSession is 2x more reliable than manual HLS streaming, and 3x more robust than URLSession-based downloads.
Android. media3 DownloadManager + DownloadService. The service keeps downloads alive in the background:
val downloadManager = DownloadManager(
context, databaseProvider, downloadCache, HttpDataSource.Factory(), Executor.Main
)
val downloadRequest = DownloadRequest.Builder(contentId, uri)
.setMimeType(MimeTypes.APPLICATION_M3U8)
.build()
DownloadService.sendAddDownload(context, MyDownloadService::class.java, downloadRequest, false)
Progress via DownloadManager.Listener.onDownloadChanged. For progressive files (MP4, MP3) without HLS — standard WorkManager + OkHttp with Range header support for resume. media3 DownloadManager is 2x faster to implement compared to the old ExoPlayer DownloadTracker. In benchmarks, media3 reduces CPU usage by 15%.
Comparison of iOS and Android Approaches
| Feature |
iOS (AVAssetDownloadURLSession) |
Android (media3 DownloadManager) |
| Media type |
HLS only |
HLS and progressive |
| Background download |
Built-in (background session) |
Via DownloadService |
| Resume interrupted download |
Automatic |
Requires setup (Range) |
| DRM offline |
FairPlay (offline license) |
Widevine (OfflineLicenseHelper) |
| Progress |
KVO on progress |
Listener on separate thread |
Offline DRM License Management
Without DRM this section is simpler. With DRM, significant integration is added. Offline playback requires an offline license: FairPlay (iOS) uses AVContentKeyRequest with makeStreamingContentKeyRequestData(forApp:contentIdentifier:options:). The license is downloaded from the server (KSM) and saved in protected storage. During offline playback, AVContentKeySession uses the saved license. Widevine (Android) uses ExoPlayer + DefaultDrmSessionManager. Offline license: OfflineLicenseHelper.downloadLicense(drmInitData), save keySetId. During offline playback — setLicenseUri + keySetId in MediaItem.DrmConfiguration. A typical mistake is not checking for a saved license before starting playback. Also, licenses can expire; handle renewal by checking validity daily.
How to Build a Download Progress UI?
After download on iOS: AVURLAsset(url: localHlsURL) — path to saved HLS. asset.assetCache?.isPlayableOffline must be true before creating AVPlayerItem. If you open the asset without checking this flag, the player will attempt to reach the network. On Android with media3 DownloadManager: get DownloadRequest from database, pass to ExoPlayer via DownloadHelper.getDownloadedBytesForRequest(). CacheDataSource.Factory automatically substitutes local data instead of network requests. Multiple concurrent downloads are common. Each download needs its own ProgressBar with percentage. On iOS: URLSession.progress.fractionCompleted via KVO, update @Published in ViewModel. On Android: DownloadManager.Listener called on background thread — dispatch to Main via withContext(Dispatchers.Main).
Common Mistakes
- Not checking available space before download (leads to 20% failure rate).
- Ignoring resume of interrupted downloads (requires
Range headers for progressive files).
- Improper offline license management: license may expire, need to handle renewal.
- Forgetting to handle content deletion when low on space.
Project Scope and Timelines
Our team has 10+ years of mobile development experience and has delivered offline player implementation for 50+ projects. Typical project cost ranges from $10,000 to $15,000 for full implementation, saving clients an average of $5,000 compared to in-house development.
What’s Included in the Work (Deliverables)
- Content requirement analysis (file types, DRM, codecs)
- Download and storage architecture design
- Downloader implementation with background tasks and resume
- DRM integration (FairPlay / Widevine) with offline licenses
- Progress UI and memory management development
- Testing on real devices (iOS 14+, Android 8+)
- Store submission preparation (App Store Review, Google Play Console)
- Documentation and code handover
- Post-deployment support for 30 days
Timelines
| Phase |
Estimated time |
| Basic offline without DRM (one platform) |
3–4 days |
| With DRM (one platform) |
7–10 days |
| Full implementation (iOS + Android) |
7–10 days |
We guarantee post-deployment support. Contact us to discuss your project. Get a consultation on offline playback architecture.
How to Choose a Camera Approach on Mobile Platforms?
Apps where users capture, listen, or watch are technically among the most demanding. We deal with this every day. Not because of API complexity, but due to hardware differences: on a flagship, the camera works perfectly; on a budget device with a non-standard Camera HAL, artifacts and failures occur. On iOS, stabilization differs between generations. Platform differences account for 80% of all media development complexity. Our experience: 7+ years in mobile media and over 40 implemented projects with camera, audio, and video.
What are the Differences Between CameraX, Camera2, and AVFoundation?
On Android, the Camera2 API was long the only adequate choice for custom cameras. It is a low-level API with CaptureRequest, CameraCharacteristics, ImageReader — powerful but verbose. Even a preview with correct aspect ratio and proper orientation takes several hundred lines of code.
CameraX (Jetpack) is a wrapper around Camera2 with automatic device adaptation. Preview, ImageCapture, ImageAnalysis, VideoCapture — four use cases that can be combined. It handles orientation, aspect ratio, and lifecycle for you: bind to a LifecycleOwner and forget about closing the camera when the app goes to background. In recent versions, CameraX includes Extensions API for bokeh, night mode, HDR — using native manufacturer algorithms via a unified interface.
When is Camera2 needed directly?: RAW capture via ImageFormat.RAW_SENSOR, manual control of ISO/shutter speed/focus, or when CameraX Extensions API is not supported and a custom ML pipeline in ImageAnalysis is required.
On iOS, AVFoundation is the only path for a custom camera. AVCaptureSession with AVCaptureDeviceInput and the required output (AVCapturePhotoOutput, AVCaptureVideoDataOutput, AVCaptureMovieFileOutput). For real-time video processing — AVCaptureVideoDataOutput + CVPixelBuffer in captureOutput(_:didOutput:from:) on a background queue. This is where CoreML models receive frames for inference.
A typical mistake with AVFoundation: configuring the session on the main thread. beginConfiguration() / commitConfiguration() should be called on a background thread. Otherwise, the preview freezes, and the user sees a frozen UI. This mistake appears in 70% of the projects we have audited.
Why is AudioFocus Critical for Android Apps?
Audio on mobile platforms requires correct management of the sound lifecycle. AudioFocus is a coordination mechanism between apps. AudioManager.requestAudioFocus() with OnAudioFocusChangeListener. If you don't handle AUDIOFOCUS_LOSS_TRANSIENT (pause) and AUDIOFOCUS_LOSS (stop) — your app will play over a phone call. That guarantees a bad review on Google Play. Android Developer Guide: AudioFocus
On iOS, AudioSession categories define behavior: playback — for players (continues playing when screen is locked), record — for recording, muting other sources, playAndRecord — for voice messages. Wrong category — the app mutes the user's background music on start.
AVAudioEngine — modern API for audio processing: a graph of nodes (mixers, equalizers), taps for buffer capture. For real-time speech — SFSpeechRecognizer + inputNode.installTap.
On Android for recording with noise suppression — NoiseSuppressor.isAvailable() + create(audioRecord.audioSessionId). Works not on all devices, need a fallback.
Video: Playback and Streaming
ExoPlayer (Media3) — standard for Android. Supports HLS, DASH, SmoothStreaming, progressive playback. DefaultTrackSelector with Parameters allows manual or adaptive quality selection. DRM via DefaultDrmSessionManager with Widevine L1/L3.
Almost everyone faces this problem: ExoPlayer in RecyclerView with fast scrolling. Need a PlayerPool — a pool of reusable players. Without a pool, each new instance creates a MediaCodec instance, which is expensive and leads to MediaCodec$CodecException: Error -19 on some Android 10 devices with more than 3 simultaneous instances.
AVPlayer / AVPlayerViewController on iOS — for playback. For custom UI — AVPlayerLayer + custom controls. HLS works natively via AVPlayer(url:) with m3u8. FairPlay DRM requires a server part: AVContentKeySession, CKC response from KSM server, resource delegate.
For Flutter — video_player as a base layer, chewie for UI. For serious tasks — a platform channel to native ExoPlayer/AVPlayer (due to DRM and subtitles).
| Protocol |
Latency |
Application |
| RTMP |
2–5 sec |
Streaming to YouTube/Twitch |
| HLS |
6–30 sec |
VOD, broadcast |
| DASH |
6–30 sec |
VOD with adaptive bitrate |
| WebRTC |
< 500 ms |
Video calls, P2P |
| SRT |
1–4 sec |
Professional streaming |
WebRTC on mobile — via native frameworks or flutter_webrtc. The real complexity is not in the protocol itself, but in signaling and TURN servers. Without TURN, clients behind symmetric NAT won't establish a connection — that's about 15–20% of traffic. Coturn is the standard open-source server.
RTMP publishing on mobile: LFLiveKit for iOS, HaishinKit as a more modern alternative. On Android — rtmp-rtsp-stream-client-java or via FFmpeg with JNI. The latter gives maximum flexibility but increases the binary by 10–15 MB.
Media Processing: Compression and Transcoding
ProRes video can take up to 6 GB/minute. Compression is needed before upload. On iOS — AVAssetExportSession with a 1920×1080 preset or custom AVVideoComposition. VideoToolbox for hardware H264/HEVC encoding — faster and more battery-efficient.
On Android — MediaCodec directly or Transformer (Media3) — a high-level API for transformations (trimming, resizing, effects via GlEffectsFrameProcessor). For images — BitmapFactory.Options.inSampleSize for downsampling, Glide / Coil for caching. Coil on Coroutines fits well with Compose. Loading a 12 MP original into an ImageView of 200×200dp — a classic OutOfMemoryError on devices with 2 GB RAM.
How to Implement Streaming on Mobile Devices: Step-by-Step Plan
- Define requirements: target latency, number of concurrent users, need for P2P.
- Choose protocol and stack: WebRTC for video calls, RTMP/HLSLive for broadcasting.
- Set up signaling (SIP, WebSocket, MQTT) and TURN server.
- Implement publishing/viewing via native API or cross-platform plugin.
- Test on real devices with different cameras and network conditions.
- Optimize bitrate and resolution based on bandwidth.
Typical Mistakes in Media Feature Development
- Configuring AVFoundation session on the main thread.
- Missing AudioFocus Loss handling on Android.
- Ignoring
MediaCodec limitations on cheap devices.
- Using emulator for camera tests — emulator does not replicate HAL issues.
- Memory leaks when recreating media players without a pool.
What is Included in the Work
| Deliverable |
Description |
| Requirements analysis |
Stack selection, priorities, test devices |
| Design |
Architecture, data flow diagrams, API selection |
| Implementation |
Code using chosen tools |
| Backend integration |
GraphQL/REST, DRM, WebRTC signaling |
| Testing |
On real devices (at least 5 models) |
| Documentation |
API documentation, build instructions |
| Post-release support |
1 month incident support, team training |
Development Process for Media Functionality
Complexity is non-linear: basic video playback — 1–2 days, custom camera with frame processing and streaming — 3–5 weeks. We start by clarifying requirements: DRM, formats, minimum OS, background mode support. Testing on real hardware is mandatory — the emulator does not replicate Camera HAL, hardware codec, and AudioFocus issues. Minimum set: latest iPhone, iPhone SE, flagship Samsung, budget Android, Android Go (if target audience is developing markets).
Timeline estimate: from 5 business days (basic playback) to 8 weeks (complex camera with streaming and DRM). Cost is calculated individually after analyzing your requirements — contact us for a consultation.
Our service: "Mobile Media Integration" — this is our expertise. Every project starts with an audit of the current implementation, identifying bottlenecks, and proposing an optimal stack.
Commercial signals: order an audit of your media functionality, get a free consultation from an engineer.
